Artificial kidneys have been used for almost 50 years to treat patients with different forms of renal failure. The artificial kidney (dialysis machine) removes unwanted substances from the blood by diffusion. A patient's blood is passed through channels bounded by a porous, semi-permeable membrane that allows the free diffusion in both directions of all plasma constituents except the plasma proteins. Erythrocytes and other cellular components of blood cannot pass through the membrane. The other side of the membrane is exposed to the dialyzing fluid which carries away the unwanted materials.If the concentration of a material in the blood is greater than in the dialyzing fluid, there will be a net flow of the material from the plasma to the dialyzing fluid. If the concentration of a material in the blood is less than in the dialyzing fluid, there will be a net flow of the material from the dialyzing fluid into the blood. The composition of normal plasma, plasma in an individual suffering renal failure, and dialyzing fluid are shown in Table 1.Table 1Dialysis replaces some functions of the kidneys and attempts to correct the effects of renal failure. For example, patients with renal failure develop acidosis due to a buildup of metabolically produced acids in the circulation. Without dialysis, the pH of the blood will drop and coma may occur. Dialyzing fluid contains a relatively high concentration of bicarbonate which diffuses into the circulation and neutralizes the acid.The semi-permeable membrane of the dialysis machine functions in a manner most analogous to which part of the kidney?
Answer(s): A
The glomerulus functions like a sieve, allowing the filtration (movement from the circulation into the nephron tubule) of small molecules while blocking the filtration of the plasma proteins. The semi-permeable membrane serves an analogous function in the dialysis machine.Choice B is incorrect because the ureter is merely a tube connecting the kidney to the bladder.Choice C is incorrect because the descending loop of Henle endothelium does not serve a filtration function.The primary action of the descending loop is reabsorption of water.Choice D is incorrect because the vasa recta are the capillaries that supply nutrients to the nephron.
Artificial kidneys have been used for almost 50 years to treat patients with different forms of renal failure. The artificial kidney (dialysis machine) removes unwanted substances from the blood by diffusion. A patient's blood is passed through channels bounded by a porous, semi-permeable membrane that allows the free diffusion in both directions of all plasma constituents except the plasma proteins. Erythrocytes and other cellular components of blood cannot pass through the membrane. The other side of the membrane is exposed to the dialyzing fluid which carries away the unwanted materials.If the concentration of a material in the blood is greater than in the dialyzing fluid, there will be a net flow of the material from the plasma to the dialyzing fluid. If the concentration of a material in the blood is less than in the dialyzing fluid, there will be a net flow of the material from the dialyzing fluid into the blood. The composition of normal plasma, plasma in an individual suffering renal failure, and dialyzing fluid are shown in Table 1.Table 1Dialysis replaces some functions of the kidneys and attempts to correct the effects of renal failure. For example, patients with renal failure develop acidosis due to a buildup of metabolically produced acids in the circulation. Without dialysis, the pH of the blood will drop and coma may occur. Dialyzing fluid contains a relatively high concentration of bicarbonate which diffuses into the circulation and neutralizes the acid.A patient with renal failure has nephrons which lack the ability to actively secrete or reabsorb any substances. Which of the following actions will the patient's kidney still be able to perform?
Salt is removed from the blood by filtration at the glomerulus. Recall that the fluid in Bowman's capsule is isotonic to plasmA. Without reabsorption or secretion, isotonic urine can still be produced.Choice B is incorrect because production of hypertonic urine requires the concentration gradient between the medulla and cortex of the kidney. This gradient is generated by active secretion and reabsorption.Choice C is incorrect because production of hypotonic urine requires active reabsorption and secretion.Choice D is incorrect because amino acids are filtered and then actively reabsorbed in the proximal convoluted tubule.
Artificial kidneys have been used for almost 50 years to treat patients with different forms of renal failure. The artificial kidney (dialysis machine) removes unwanted substances from the blood by diffusion. A patient's blood is passed through channels bounded by a porous, semi-permeable membrane that allows the free diffusion in both directions of all plasma constituents except the plasma proteins. Erythrocytes and other cellular components of blood cannot pass through the membrane. The other side of the membrane is exposed to the dialyzing fluid which carries away the unwanted materials.If the concentration of a material in the blood is greater than in the dialyzing fluid, there will be a net flow of the material from the plasma to the dialyzing fluid. If the concentration of a material in the blood is less than in the dialyzing fluid, there will be a net flow of the material from the dialyzing fluid into the blood. The composition of normal plasma, plasma in an individual suffering renal failure, and dialyzing fluid are shown in Table 1. Table 1Dialysis replaces some functions of the kidneys and attempts to correct the effects of renal failure. For example, patients with renal failure develop acidosis due to a buildup of metabolically produced acids in the circulation. Without dialysis, the pH of the blood will drop and coma may occur. Dialyzing fluid contains a relatively high concentration of bicarbonate which diffuses into the circulation and neutralizes the acid.All of the following are removed from the plasma by dialysis EXCEPT:
Answer(s): D
By comparing the concentration of a material in the dialyzing fluid with the concentration in plasma, we can determine the net flow by passive diffusion through the semi-permeable membrane. Of all of the choices, only glucose has a higher concentration in the dialyzing fluid than in the plasma (with or without renal failure). Thus, glucose will not be removed from the plasma by dialysis.Choice A is incorrect because the concentration of Na+ in the dialyzing fluid is 133 mEq/L which is less than the concentration in plasma (142 mEq/L). Sodium will be removed.Choice B is incorrect because the concentration of K+ (1.0 mEq/L) is much lower than the concentration in the plasma.Choice C is incorrect because there is no urea in the dialyzing fluid. One of the primary functions of dialysis is the removal of urea from the circulation.
Artificial kidneys have been used for almost 50 years to treat patients with different forms of renal failure. The artificial kidney (dialysis machine) removes unwanted substances from the blood by diffusion. A patient's blood is passed through channels bounded by a porous, semi-permeable membrane that allows the free diffusion in both directions of all plasma constituents except the plasma proteins. Erythrocytes and other cellular components of blood cannot pass through the membrane. The other side of the membrane is exposed to the dialyzing fluid which carries away the unwanted materials.If the concentration of a material in the blood is greater than in the dialyzing fluid, there will be a net flow of the material from the plasma to the dialyzing fluid. If the concentration of a material in the blood is less than in the dialyzing fluid, there will be a net flow of the material from the dialyzing fluid into the blood. The composition of normal plasma, plasma in an individual suffering renal failure, and dialyzing fluid are shown in Table 1. Table 1Dialysis replaces some functions of the kidneys and attempts to correct the effects of renal failure. For example, patients with renal failure develop acidosis due to a buildup of metabolically produced acids in the circulation. Without dialysis, the pH of the blood will drop and coma may occur. Dialyzing fluid contains a relatively high concentration of bicarbonate which diffuses into the circulation and neutralizes the acid.Healthy kidneys secrete the hormone renin in response to decreased arterial pressure. Renin secretion leads to aldosterone secretion by the adrenal cortex. The body would most likely respond to ingestion of a large volume of isotonic solution by:
Answer(s): B
The question stem states that kidneys secrete renin in response to decreased arterial pressure. Ingesting a large quantity of isotonic solution would tend to increase the arterial pressure. This would lead to a decrease in renin production and a consequent decrease in aldosterone secretion. Decreased aldosterone secretion would decrease sodium reabsorption which is accompanied by reabsorption of water. Decreasing reabsorption of water tends to increase water excretion and reduce blood pressure. This is shown in the flow chart below: Choice A is incorrect because sodium reabsorption would decrease.Choice C is incorrect because renin production would decrease.Choice D is incorrect because renin production would decrease.
Which of the following reactants should be used to form the product shown below?
This question is primarily testing your knowledge of nomenclature. Reacting an alkanoyl halide with an alcohol will lead to formation of an ester, as shown. Note that we have added 3 carbons to our molecule, and so the unknown reactant must have three carbons. Propanol is the only three carbon choice, and the only alcohol.
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